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288              PROFESSOR SCOTT ON  POEBROTSERIUM            CHAP.

and the greater part of a radius and ulna belonging to one
individual, and most portions of the hind-limbs in other specimens.
The one species, P. petersoni, was about the size of a te jack
rabbit/' and is late Eocene (Uinta formation) and American in
range. The teeth of this mammal are the typical forty-four, and
the canines are not pronounced,, being incisiform in shape. In
the skull the nasals overhang, as in the genus Poebrotherium. The
orbit is not closed by bone. There is in this ancient Camel a trace
of the supra-orbital notch so characteristic of the Camel tribe.
" The vertebrae resemble those of the modem Lamas closely In
their general proportions," The lumbars have the usually Cameloid
formula of 7. This genus has but two functional toes on the hind-

FIG. 150.—Skull of Poebrotherium tmlsoni.     I1, I2, 1s, Incisors 1-3.     x*.
(After Wortman.)
feet, the second and fifth being reduced to vestiges. It is interest-
ing to note that the radius and ulna appear to remain distinct,
except in very old animals, in which they come to be co-ossified
in the middle only, thus foreshadowing their complete union in the
next genus, Poebroth&rium. The present genus, moreover, as well
as Poebrotherium, was distinctly imguligrade; it has not acquired
the characteristic phalangigrade mode of progression of die modern
types of Camels.
The American and Oligocene JPoebrotTierium has been recently
and exhaustively studied by Professor Scott.1 It was considerably
smaller than a X*ama. Its neck was long as compared with other
Artiodactyles, but still shorter than that of the Lama. It was a
lightly-built, graceful creature, with apparently some external
likeness to a Xama. It is an important fact to notice that at this
1 ** Osteology of P&^ro&^wium," Jtwrn* Mvrph. r. 1891, p. 1.